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3 pages, 165 KiB

Open AccessEditorial

Casting and Forming of Advanced Aluminum Alloys

by Hélder Puga

Metals 2020, 10(4), 494; https://doi.org/10.3390/met10040494 - 9 Apr 2020

Cited by 8 | Viewed by 3410

Abstract

The automotive and aeronautical industry´s response to the environmental impact provoked by gas emissions and consumer expectations has driven aluminum alloy casting changes in recent years [...] Full article

(This article belongs to the Special Issue Casting and Forming of Advanced Aluminum Alloys)

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7 pages, 3754 KiB

Open AccessCommunication

Role of Roll Separating Force in High-Speed Twin-Roll Casting of Aluminum Alloys

by Min-Seok Kim, Hyoung-Wook Kim, Su-Hyeon Kim and Shinji Kumai

Metals 2019, 9(6), 645; https://doi.org/10.3390/met9060645 - 3 Jun 2019

Cited by 13 | Viewed by 4259

Abstract

The role of the roll separating force in the high-speed twin-roll casting of aluminum alloys was examined. In horizontal-type twin-roll casting, as the casting speed increased upon decreasing the roll separating force, the strip texture changed from a shear and rolling texture to [...] Read more.

The role of the roll separating force in the high-speed twin-roll casting of aluminum alloys was examined. In horizontal-type twin-roll casting, as the casting speed increased upon decreasing the roll separating force, the strip texture changed from a shear and rolling texture to a random texture. Direct temperature measurements during high-speed twin-roll casting showed that the roll separating force played a significant role in maintaining a good contact between the strip and the roll surface. This resulted in a high cooling rate around the roll nip and enabled the fabrication of a sound strip with a fine microstructure. Moreover, the high casting speed and lowered roll separating force gave a band structure consisting of fine globular grains in the mid-thickness region of the strip, which could be considered beneficial in the formation of a well-dispersed center segregation. Full article

(This article belongs to the Special Issue Casting and Forming of Advanced Aluminum Alloys)

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9 pages, 3417 KiB

Open AccessArticle

Effects of Prebending Radii on Microstructure and Fatigue Performance of Al-Zn-Mg-Cu Aluminum Alloy after Creep Age Forming

by Dalian Yang, Jingjing Miao, Fanyu Zhang, Zhuo Fu and Yilun Liu

Metals 2019, 9(6), 630; https://doi.org/10.3390/met9060630 - 30 May 2019

Cited by 6 | Viewed by 3091

Abstract

A series of creep age forming experiments were carried out on 7075 aluminum alloy with different prebending radii at 443 K for 10 h. The hardness, tensile properties and high cycle fatigue performance of the alloy after creep age forming were obtained. In [...] Read more.

A series of creep age forming experiments were carried out on 7075 aluminum alloy with different prebending radii at 443 K for 10 h. The hardness, tensile properties and high cycle fatigue performance of the alloy after creep age forming were obtained. In addition, the microstructure and fatigue fracture of the alloy were observed by transmission electron microscopy (TEM) and scanning electron microscope (SEM). The results show that with the increase of the prebending radius, the hardness, strength and elongation of the alloy increased; meanwhile, the conditional fatigue limit increased, the size of precipitated phase decreased and the quantity increased, while the width of precipitate free zone decreased. Full article

(This article belongs to the Special Issue Casting and Forming of Advanced Aluminum Alloys)

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11 pages, 6056 KiB

Open AccessArticle

The Role of Acoustic Pressure during Solidification of AlSi7Mg Alloy in Sand Mold Casting

by H. Puga, J. Barbosa and V. H. Carneiro

Metals 2019, 9(5), 490; https://doi.org/10.3390/met9050490 - 27 Apr 2019

Cited by 9 | Viewed by 3447

Abstract

New alloy processes have been developed and casting techniques are continuously evolving. Such constant development implies a consequent development and optimization of melt processing and treatment. The present work proposes a method for studying the influence of acoustic pressure in the overall refinement [...] Read more.

New alloy processes have been developed and casting techniques are continuously evolving. Such constant development implies a consequent development and optimization of melt processing and treatment. The present work proposes a method for studying the influence of acoustic pressure in the overall refinement of sand cast aluminum alloys, using and correlating experimental and numerical approaches. It is shown that the refinement/modification of the α-Al matrix is a consequence of the acoustic activation caused in the liquid metal directly below the face of the acoustic radiator. Near the feeder, there is a clear homogeneity in the morphology of the α-Al with respect to grain size and grain circularity. However, the damping of acoustic pressure as the melt is moved away from the feeder increases and the influence of ultrasound is reduced, even though the higher cooling rate seems to compensate for this effect. Full article

(This article belongs to the Special Issue Casting and Forming of Advanced Aluminum Alloys)

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13 pages, 3396 KiB

Open AccessFeature PaperArticle

Optimizing the Conditions of Metal Solidification with Vibration

by Olga Kudryashova, Marina Khmeleva, Pavel Danilov, Vladislav Dammer, Alexander Vorozhtsov and Dmitry Eskin

Metals 2019, 9(3), 366; https://doi.org/10.3390/met9030366 - 21 Mar 2019

Cited by 13 | Viewed by 5594

Abstract

Vibration treatment of solidifying metals results in improvement in the ingot structure. There is a need to study this process not only because of the practical potential of vibration treatment but also due to the lack of understanding the process. An important practical [...] Read more.

Vibration treatment of solidifying metals results in improvement in the ingot structure. There is a need to study this process not only because of the practical potential of vibration treatment but also due to the lack of understanding the process. An important practical challenge is to find optimal conditions for liquid metal processing. In this paper, the authors consider a solidification process in the particular case of a cylindrical chill mold with vibration as a solution of the Stefan problem. An integral value of mechanical stresses in the melt during solidification is considered as an efficiency criterion of vibration treatment. A dependence of this value on the vibration frequency and amplitude is obtained through solving the Stefan problem numerically. The solution allows one to find the optimal vibration frequency and amplitude. We verified the numerical solution with experimental data obtained upon vibration treatment of aluminum melt under different conditions. The experimentally found optimal conditions for metal processing were similar to those proposed in theory, i.e., a vibration frequency of about 60 Hz and an amplitude of about 0.5 mm. Full article

(This article belongs to the Special Issue Casting and Forming of Advanced Aluminum Alloys)

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15 pages, 3321 KiB

Open AccessArticle

Microstructural Evaluation and Corrosion Resistance of Semisolid Cast A356 Alloy Processed by Equal Channel Angular Pressing

by Mohamed Abdelgawad Gebril, Mohd Zaidi Omar, Intan Fadhlina Mohamed and Norinsan Kamil Othman

Metals 2019, 9(3), 303; https://doi.org/10.3390/met9030303 - 8 Mar 2019

Cited by 12 | Viewed by 3158

Abstract

As-cast and semisolid casting using a cooling slope A356 alloy were processed by equal channel angular pressing (ECAP) for Si and grain refinement. The ECAP was conducted at room temperature in a mold, with a channel angle of 120°, and this resulted in [...] Read more.

As-cast and semisolid casting using a cooling slope A356 alloy were processed by equal channel angular pressing (ECAP) for Si and grain refinement. The ECAP was conducted at room temperature in a mold, with a channel angle of 120°, and this resulted in a significant size reduction of grain and Si particles from 170.5 and 4.22 to 23.12 and 0.71 µm, respectively, after six passes of heat-treated cooling slope casting, using the ECAP process. The hardness increased with ECAP processing, from 61 HV, for the as-cast alloy, to 134 Hv, after six passes of heat-treated cooling slope casting. The corrosion resistance of the alloy improved, from 0.042 to 0.0012 mmy⁻¹, after the ECAP process. In this work both the strength and corrosion resistance of the ECAPed A356 alloys were improved with the application of the cooling slope process than without (i.e., from the as-cast condition). Full article

(This article belongs to the Special Issue Casting and Forming of Advanced Aluminum Alloys)

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8 pages, 6547 KiB

Open AccessArticle

Joint Effect of Ultrasonic Vibrations and Solid Metal Addition on the Grain Refinement of an Aluminium Alloy

by Dmitry Eskin and Feng Wang

Metals 2019, 9(2), 161; https://doi.org/10.3390/met9020161 - 1 Feb 2019

Cited by 10 | Viewed by 3649

Abstract

It is well known that it takes some time for the solid phase to completely dissolve upon melting, especially inside the defects of insoluble particles, e.g. oxides. Until then the oxides remain active solidification substrates in the case of subsequent solidification. It is [...] Read more.

It is well known that it takes some time for the solid phase to completely dissolve upon melting, especially inside the defects of insoluble particles, e.g. oxides. Until then the oxides remain active solidification substrates in the case of subsequent solidification. It is also known that ultrasonic melt treatment causes grain refinement through activation and dispersion of solidification substrates (one of the mechanisms) and also accelerates the dissolution of solid metal in the melt. In this study we combine these effects and demonstrate that the introduction of an alloy rod into the matrix melt of the same composition results in significant grain refinement, this effect is increased by the ultrasonic vibration of the rod. The achieved grain size is comparable to that obtained by a standard Al–Ti–B grain refiner. All samples were cast using a standard TP-1 mould to enable correct comparison. The effects of the temperature range of the rod introduction as well as the application of ultrasonic vibrations are discussed. Full article

(This article belongs to the Special Issue Casting and Forming of Advanced Aluminum Alloys)

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21 pages, 12175 KiB

Open AccessArticle

Superplastic Behavioral Characteristics of Fine-Grained 5A70 Aluminum Alloy

by Sheng Li, Zhongguo Huang and Shunyao Jin

Metals 2019, 9(1), 62; https://doi.org/10.3390/met9010062 - 10 Jan 2019

Cited by 8 | Viewed by 3351

Abstract

A fine-grained 5A70 alloy sheet was obtained through a combination of rolling and heat treatment, with a total deformation reduction of 90% and an average grain size of 8.48 μm. The alloy was studied at 400, 450, 500, and 550 °C and exhibited [...] Read more.

A fine-grained 5A70 alloy sheet was obtained through a combination of rolling and heat treatment, with a total deformation reduction of 90% and an average grain size of 8.48 μm. The alloy was studied at 400, 450, 500, and 550 °C and exhibited excellent elongation-to-failures of 205, 321, 398, and 437% with coefficients for the strain rate sensitivity of 0.42, 0.40, 0.47 and 0.46, respectively. Electron backscatter diffraction (EBSD) results revealed that the massive grain boundaries were high angle boundaries, suggesting that boundary sliding and grain rotation occurred during superplastic deformation. The X-ray diffraction (XRD) and energy dispersive spectrometer (EDS) results indicated that the compositions were the Al₆(MnFe) and Mg-rich phase particles of the deformed 5A70 alloy. In addition, the weakening of the pinning effect led to abnormal grain growth at 500 and 550 °C, resulting in strain hardening. Transmission electron microscopy (TEM) examinations demonstrated that the applied stress at the head of the precipitated particles and/or grain boundaries exceeded the matrix-structure-promoted cavity nucleation. Cavities grew, interlinked, and coalesced, which resulted in crack formation that eventually led to superplastic fractures. Filaments formed at the fracture surfaces because of second phase precipitation at grain boundaries and the formation of Mg-rich oxides. Full article

(This article belongs to the Special Issue Casting and Forming of Advanced Aluminum Alloys)

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15 pages, 5111 KiB

Open AccessArticle

Cavity Behavior of Fine-Grained 5A70 Aluminum Alloy during Superplastic Formation

by Sheng Li, Shunyao Jin and Zhongguo Huang

Metals 2018, 8(12), 1065; https://doi.org/10.3390/met8121065 - 14 Dec 2018

Cited by 10 | Viewed by 3253

Abstract

The study of the exact physical mechanism of cavity nucleation and growth is significant in terms of predicting the extent of internal damage following superplastic deformation. The 5A70 alloy was processed by cold rolling for 14 passes with a total reduction deformation of [...] Read more.

The study of the exact physical mechanism of cavity nucleation and growth is significant in terms of predicting the extent of internal damage following superplastic deformation. The 5A70 alloy was processed by cold rolling for 14 passes with a total reduction deformation of 90% (20–2 mm) and the heat treatment was inserted at a thickness of 10 and 5 mm at 340 °C for 30 min. The superplastic tensile tests were performed at 400, 450, 500, 550 °C and the initial strain rate was 1 × 10⁻³ s⁻¹. Cavities were observed at the head of the particle and the interface of the grain boundaries. It is suggested that the cavity was nucleated during the sliding/climbing of the dislocations, due to the precipitate pinning effect and the impeding grain boundary during grain boundary sliding (GBS). In this study, the results demonstrated a clear transition from diffusion growth to superplastic diffusion growth and plastic-controlled growth at a cavity radius larger than 1.52 and 13.90 μm. The cavity nucleation, growth, interlinkage and coalescence under the applied stress during the superplastic deformation, as well as the crack formation and expansion during the deformation, ultimately led to the superplastic fracture. Full article

(This article belongs to the Special Issue Casting and Forming of Advanced Aluminum Alloys)

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8 pages, 1638 KiB

Open AccessArticle

Effect of a Traveling Magnetic Field on Micropore Formation in Al-Cu Alloys

by Yanjin Xu, Lijun Wei, Baoshuai Han, Enyu Guo, Mingyue Wang and Yanqing Su

Metals 2018, 8(6), 448; https://doi.org/10.3390/met8060448 - 12 Jun 2018

Cited by 4 | Viewed by 3589

Abstract

The effect of traveling magnetic fields (TMFs) on the grain and micro-pore formation in an Al alloy was studied by scanning electron microscope and X-ray microtomography in this work. The results show that with the increasing magnetic flux density, the three-dimensional morphology of [...] Read more.

The effect of traveling magnetic fields (TMFs) on the grain and micro-pore formation in an Al alloy was studied by scanning electron microscope and X-ray microtomography in this work. The results show that with the increasing magnetic flux density, the three-dimensional morphology of the micro-pores transformed from dendrite to a relatively equiaxed structure. Quantified results show that both the micro-pore volume fraction and the average grain size of the primary phase decreased as the TMF density increased. The analyses show that the forced convection induced by TMF can break the dendrites, refine the grain size, and promote the liquid feeding, leading to the decrease in the volume fraction of the porosity and improved mechanical property. The TMF performed at different stages during solidification reveal that the maximum effect of TMF on reducing the micro-pore formation was found when TMF was applied in the stage of nucleation and the early stage of grain growth during solidification. Full article

(This article belongs to the Special Issue Casting and Forming of Advanced Aluminum Alloys)

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13 pages, 14031 KiB

Open AccessArticle

Surface Quality Improvement of AA6060 Aluminum Extruded Components through Liquid Nitrogen Mold Cooling

by Andrea Francesco Ciuffini, Silvia Barella, Cosmo Di Cecca, Andrea Gruttadauria, Carlo Mapelli, Luca Merello, Giacomo Mainetti and Massimo Bertoletti

Metals 2018, 8(6), 409; https://doi.org/10.3390/met8060409 - 1 Jun 2018

Cited by 9 | Viewed by 5318

Abstract

6xxx aluminum alloys are suitable for the realization of both structural applications and architectural decorative elements, thanks to the combination of high corrosion resistance and good surface finish. In areas where the aesthetic aspects are fundamental, further improvements in surface quality are significant. [...] Read more.

6xxx aluminum alloys are suitable for the realization of both structural applications and architectural decorative elements, thanks to the combination of high corrosion resistance and good surface finish. In areas where the aesthetic aspects are fundamental, further improvements in surface quality are significant. The cooling of the extrusion mold via internal liquid nitrogen fluxes is emerging as an important innovation in aluminum extrusion. Nowadays, this innovation is providing a large-scale solution to obtain high quality surface finishes in extruded aluminum semi-finished products. These results are also coupled to a significant increase in productivity. The aim of the work is to compare the surface quality of both cooled liquid nitrogen molds and classically extruded products. In this work, adhesion phenomena, occurring during the extrusion between the mold and the flowing material, have been detected as the main causes of the presence of surface defects. The analysis also highlighted a strong increase in the surface quality whenever the extrusion mold was cooled with liquid nitrogen fluxes. This improvement has further been confirmed by an analysis performed on the finished products, after painting and chromium plating. This work on the AA6060 alloy has moreover proceeded to roughness measurements and metallographic analyses, to investigate the eventual occurrence of other possible benefits stemming from this new extrusion mold cooling technology. Full article

(This article belongs to the Special Issue Casting and Forming of Advanced Aluminum Alloys)

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